United States

Artificially made, geometrically frustrated arrays of interacting magnetic nanostructures offer a remarkable playground for exploring spin ice physics experimentally [1-3]. Initially designed to capture the low-energy properties of highly frustrated magnets [4,5], artificial spin ices became in the past decade a powerful lab-on-chip platform in which to investigate cooperative magnetic phenomena and exotic states of matter. Since their introduction about fifteen years ago, the interest in artificial spin ice systems largely broadened, and the term now covers a wide range of physical phenomena and systems extending well beyond artificial ice-like magnets. Besides fundamental works, many studies were also conducted recently on the applicability of artificial spin ice geometries in magnetic architectures, in which the micromagnetic degree of freedom, spin wave excitations or topological magnetic pseudo-charges for example are envisioned as carriers for information transfer, storage and processing [6-8]. The richness of this fast evolving research field is certainly the variety of expertises and scientific backgrounds gathered within a single community, with scientists working in different, sometimes separated, areas of condensed matter magnetism, spreading from nanomagnetism and spintronics to frustrated magnetism and statistical mechanics. In this presentation, recent advances in the field will be overviewed and potential routes for future works will be discussed.&lt;br&gt;

**References:**&lt;br&gt;

[1] C. Nisoli, R. Moessner and P. Schiffer, Rev. Mod. Phys. 85, 1473 (2013).&lt;br&gt;
[2] N. Rougemaille and B. Canals, Eur. Phys. J B 92, 62 (2019).&lt;br&gt;
[3] S. H. Skjærvø, C. H. Marrows, R. L. Stamps and L. J. Heyderman Nat. Rev. Phys. 2, 13 (2020).&lt;br&gt;
[4] M. Tanaka et al., J. Appl. Phys. 97, 10J710 (2005); Phys. Rev. B 73, 052411 (2006).&lt;br&gt;
[5] R. F. Wang et al., Nature 439, 303 (2006).&lt;br&gt;
[6] S. Gliga, E. Iacocca and O. G. Heinonen, APL Mater. 8, 040911 (2020).&lt;br&gt;
[7] M. T. Kaffash, S. Lendinez and M. B. Jungfleisch, Phys. Lett. A 402, 127364 (2021).&lt;br&gt;
[8] J. C. Gartside et al., Nat. Nanotech. 17, 460 (2022).


MMM 2022

Artificial spin ice: a rich platform for condensed matter magnetism

Artificially made, geometrically frustrated arrays of interacting magnetic nanostructures offer a remarkable playground for exploring spin ice physics experimentally [1-3]. Initially designed to capture the low-energy properties of highly frustrated magnets [4,5], artificial spin ices became in the past decade a powerful lab-on-chip platform in which to investigate cooperative magnetic phenomena and exotic states of matter. Since their introduction about fifteen years ago, the interest in artificial spin ice systems largely broadened, and the term now covers a wide range of physical phenomena and systems extending well beyond artificial ice-like magnets. Besides fundamental works, many studies were also conducted recently on the applicability of artificial spin ice geometries in magnetic architectures, in which the micromagnetic degree of freedom, spin wave excitations or topological magnetic pseudo-charges for example are envisioned as carriers for information transfer, storage and processing [6-8]. The richness of this fast evolving research field is certainly the variety of expertises and scientific backgrounds gathered within a single community, with scientists working in different, sometimes separated, areas of condensed matter magnetism, spreading from nanomagnetism and spintronics to frustrated magnetism and statistical mechanics. In this presentation, recent advances in the field will be overviewed and potential routes for future works will be discussed. 

**References:** 

[1] C. Nisoli, R. Moessner and P. Schiffer, Rev. Mod. Phys. 85, 1473 (2013). 
[2] N. Rougemaille and B. Canals, Eur. Phys. J B 92, 62 (2019). 
[3] S. H. Skjærvø, C. H. Marrows, R. L. Stamps and L. J. Heyderman Nat. Rev. Phys. 2, 13 (2020). 
[4] M. Tanaka et al., J. Appl. Phys. 97, 10J710 (2005); Phys. Rev. B 73, 052411 (2006). 
[5] R. F. Wang et al., Nature 439, 303 (2006). 
[6] S. Gliga, E. Iacocca and O. G. Heinonen, APL Mater. 8, 040911 (2020). 
[7] M. T. Kaffash, S. Lendinez and M. B. Jungfleisch, Phys. Lett. A 402, 127364 (2021). 
[8] J. C. Gartside et al., Nat. Nanotech. 17, 460 (2022).

technical paper

#### Welcome to the 67th Annual Conference on Magnetism and Magnetic Materials, MMM 2022!

The Conference was held from October 31 to November 4 and offers both in-person and on-demand content.

MMM 2022 is sponsored jointly by AIP Publishing and the IEEE Magnetics Society. Members of the international scientific and engineering communities interested in recent developments in fundamental and applied magnetism are invited to attend and contribute to the technical sessions. The technical program will include invited and contributed papers in oral and poster sessions, invited symposia, a tutorial, and several special sessions. This Conference provides an outstanding opportunity for worldwide participants to meet their colleagues and collaborators and discuss developments in all areas of magnetism research.

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Voltage-driven ion transport modulation of magnetism (magneto-ionics) represents a significant breakthrough to enhance energy efficiency in magnetically-actuated devices. Particularly, voltage-driven oxygen ion motion in Co3O4 allows for voltage-controlled On−Off ferromagnetism, since Co3O4 (paramagnetic: Off) can be partially reduced to Co (ferromagnetic: On) by voltage actuation. This can be afterwards reversed by applying a voltage of the opposite polarity (1). The way the electric field is applied has a strong impact in the room temperature magneto-ionic motion. Specifically, in electrolyte-gated 100 nm-thick paramagnetic Co3O4 films, the oxygen magneto-ionic motion can be sped up by an order of magnitude (from 1000 to 100 s) applying the electric field through an electrochemical capacitor configuration (i.e., using, as a working electrode, an underlying conducting buffer layer beneath the Co3O4 film) rather than using an electric-double-layer transistor-like configuration (i.e., placing the electric contact at one side of the Co3O4 film as a working electrode). This is due to the better uniformity and larger strength of the electric field in the capacitor design (1,2). However, ion motion at room temperature is still too slow for applications. By reducing the Co3O4 film thickness down to 15 nm, sub-10 s ON-OFF ferromagnetism can be achieved in electrolyte-gated films (3). Remarkably, cumulative magneto-ionic effects can be generated by applying voltage pulses at frequencies as high as 100 Hz, which is the frequency at which dynamic effects of biological synapses occur. Magneto-ionics in Co3O4 can then be used to emulate synapse functionalities, including plasticity, potentiation (magnetization increase) and depression (i.e., depletion of magnetization), voltage-controlled threshold activation of ferromagnetism (i.e., spike-magnitude dependence), and learning and forgetting capabilities. The former by means of spike-rate-dependent plasticity of the generated magnetization upon pulsed voltage actuation. These features demonstrate Co3O4 magneto-ionics can be used for the design of neuromorphic-like systems (3). 

**References:** 
(1) A. Quintana, E. Menéndez, M. O. Liedke, M. Butterling, A. Wagner, V. Sireus, P. Torruella, S. Estradé, F. Peiró, J. Dendooven, C. Detavernier, P. D. Murray, D. A. Gilbert, K. Liu, E. Pellicer, J. Nogues and J. Sort, Voltage-controlled ON−OFF ferromagnetism at room temperature in a single metal oxide film, ACS Nano 12 (2018) 10291–10300 
(2) J. de Rojas, A. Quintana, A. Lopeandía, J. Salguero, J. L. Costa-Krämer, L. Abad, M. O. Liedke, M. Butterling, A. Wagner, L. Henderick, J. Dendooven, C. Detavernier, J. Sort and E. Menéndez, Boosting room-temperature magneto-ionics in a non-magnetic oxide semiconductor, Advanced Functional Materials 30 (2020) 2003704 
(3) S. Martins, J. de Rojas, Z. Tan, M. Cialone, A. Lopeandía, J. Herrero-Martín, J. L. Costa-Krämer, E. Menéndez and J. Sort, Dynamic electric-field-induced magnetic effects in cobalt oxide thin films: towards magneto-ionic synapses, Nanoscale 14 (2022) 842–852

On Off Ferromagnetism in Co3O4 by Voltage

Magnetic topological textures could serve as powerful tools in the development of next-generation spintronics devices, especially in terms of stability and energy consumption. Two-dimensional (2D) magnetic solitons such as chiral domain walls or skyrmions were mostly under focus for the last decade. Beyond these 2D textures, a new interest has risen for more complex quasi-particles that display variations over the thickness, i.e., three-dimensional (3D) objects. Examples include different skyrmion phases [1], bobbers [2] or even hopfions [3]. In this work, we show how by engineering Pt/Co/Al based multilayers with variable Co thickness, we observe the signature of new textures, called skyrmionic cocoons [4] that are only present in a fraction of the magnetic layers. Interestingly, these cocoons can coexist with more standard ‘tubular’ skyrmions going through all the multilayer as evidenced by the existence of two very different contrasts in the magnetic force microscopy (MFM) images recorded at room temperature (Fig. 1a). Moreover, the field dependence of skyrmionic cocoons has also been studied with Fourier transform holography measurements (FTH) with similar observations (Fig. 1b). FTH additionally puts forward various magnetic phase transitions as well as the existence of an attractive interaction between cocoons. The presence of these novel skyrmionic textures has also been investigated by micromagnetic simulations (Fig. 1c). The relaxed states can easily be identified with the different experimental contrasts: the columnar skyrmion tubes (resp. cocoons) corresponds to the strong contrast (resp. weak contrast). Thus, this coexistence of various magnetic textures in multilayers and the discovery of a novel magnetic texture are particularly interesting as they can open new paths for three-dimensional spintronics. 
**References** [1] A.O. Mandru et al. Nature communications 11,1 (2020)
[2] F. Zheng et al. Nature Nanotechnology 13, 451 (2018)
[3] N. Kent et al. Nature communications 12, 1 (2021)
[4] M. Grelier et al. arXiv: 2205.01172 (2022). 
![](https://s3.eu-west-1.amazonaws.com/underline.prod/uploads/markdown_image/1/image/b8a97625e75c0927f841711b49e2982a.png)

Skyrmionic 3D cocoons in magnetic multilayers

Magnetic skyrmions are candidates for information carriers in applications for racetrack memories and Brownian computers because of their topologically protected properties. The circuits to confine the skyrmions in the 1D track with the magnetic wire or the magnetic energy wall play a key role in realizing such novel devices1,2. The ratchet using magnetic energy gradient is also required for improving calculation speed in ultralow-energy-consumption operation3. Because the focused-ion-beam (FIB) technique can vary the dose of ions locally, FIB effectively makes the circuit with the energy gradient4. This study aims to verify the effect of the FIB irradiation on the confinement and diffusion of the skyrmions and to structure the magnetic-energy gradient driving the skyrmions.
We fabricated the stacking structure as Ta(5.9)|Co16Fe64B20(1.2)|Ta(0.2)|MgO(2.2)|SiO2(2.9) and microfabricated the surface of the sample by the FIB of the Ga+ source. The potential condition for skyrmion creation can be controlled spatially by adjusting the dose of ions. Fig.1 shows the observations of the irradiated region indicated with the white dash line by the magneto-optical Kerr effect (MOKE) microscope. The skyrmions in the unirradiated region appear at about 333K, and in the irradiated region at about 295.5K. Fig.2(a) shows the mean squared displacement (MSD) of the skyrmions in the irradiated region. Fig.2(b) shows the temperature dependence of the diffusion coefficient before and after FIB irradiation. FIB irradiation increases the activation energy. However, the size of the diffusion coefficient after irradiation is as large as that in the sample before irradiation as far as a higher temperature is utilized. We will discuss the possibility of sputtering and of Ga+ doping and the motion in the energy gradient. This work was supported by ULVAC, Inc., JSPS KAKENHI Grant Number JP20H05666, Japan and JST, CREST Grant Number JPMJCR20C1, Japan, and Nanotechnology Platform of MEXT, Grant Number JPMXP09 S-21-OS-0053. 
**References** [1] S. Woo, et al. Nat. Mater. 15, 501 (2016)
[2] Y. Jibiki, S. Miki, et al. Appl. Phys. Lett. 117, 082402 (2020)
[3] S. Miki, et al. J. Phys. Soc. Jpn. 90, 114703 (2021)
[4] K. Fallon, et al. small 16, 1907450 (2020) 
![](https://s3.eu-west-1.amazonaws.com/underline.prod/uploads/markdown_image/1/image/d39a2a8539e87d2efebfe4fcc418a73f.png)

Spatial control of the nucleation and dynamics of magnetic skyrmions by FIB irradiation

Magnetometers are used for navigation, the detection of submarines and underwater debris, archaeological and geological surveys, as well as in the exploration of our solar system and even in our mobile devices [1-2]. Recently, designs of solid-state quantum magnetometers have stimulated particular interest both for their small size [3], and for their potential to operate without any optical components or applied microwave fields [4].
In this work we model Optically/Electrically Detected Magnetic Resonance (ODMR/EDMR) of the Silicon vacancy in Silicon Carbide, a budding candidate for solid-state quantum magnetometry, using quantum master equations. The Silicon vacancy can be thought of as a S = 3/2 synthetic atom, and its spin states are sensitive to magnetic fields via the Zeeman effect. In ODMR, magnetic resonances of the Zeeman field are detected by extrema in the normalized photoluminescence signal when a transverse microwave field is applied. In EDMR, magnetic resonances of the Zeeman field are detected by extrema in the normalized current, generated when a conduction electron couples to the vacancy’s spin and is allowed to recombine with a valence hole in a spin-dependent manner. In both cases, the photoluminescence/current is calculated from the steady-state density matrix populations and compared to recent experimental results [5-7].
We acknowledge support from NSF DMR-1921877. 
**References** [1] Budker, D., Romalis, M., Nature Phys 3, 227–234 (2007)
[2] Ness, N.F., Space Sci Rev 11, 459–554 (1970)
[3] Kraus, H., Soltamov, V., Fuchs, F. et al., Sci Rep 4, 5303 (2014)
[4] Cochrane, C., Blacksberg, J., Anders, M. et al., Sci Rep 6, 37077 (2016)
[5] Kraus, H., Soltamov, V., Riedel, D. et al., Nature Phys 10, 157–162 (2014)
[6] Fischer, M., Sperlich, A., Kraus, H. et al., Phys. Rev. Applied 9, 054006 (2018)
[7] Cochrane, C., Kraus, H., Neudeck, P. et al., MSF 924 988-992 (2018)

Theory of a Single Si Vacancy in SiC as a Quantum Sensor of Magnetic Fields

Spintronic devices operating on spin waves (SW) can be more efficient than oxide semiconductors due to their high frequencies and low energy cost. Therefore, SW based technology may prove to be more powerful than CMOS devices due to its intrinsic characteristics [1]. Magnetic field is the primary stimuli controlling magnetism and SW dynamics. Thus, the study of the influence of the magnetic field on ferromagnetic nanostructures with different geometries is critical for modern technologies, especially for the development of 3D-magnonic circuits, where the geometric constraints generate a strong relationship between the fields of demagnetization, exchange and bias.
Recently, it has been experimentally demonstrated that the 3D network formed from the crescent-shape nanorods (CSN) is promising for development of 3D ferromagnetic systems for various applications [2]. As yet, CSN-s have not been investigated for their effect on SW spectra and manipulations in relation to magnitude and magnetic field orientation. Untypical results make our analysis relevant for future investigations and applications. In particular, we show that there are edge localized and bulk SW modes. The edge modes decouple when the external magnetic field rotates, Fig. 1. Thus, the two edges of the CSN behave as two distinct channels for SW guiding, whose frequency can be controlled by the magnetic field magnitude and orientation. Interestingly, both the polar and azimuthal rotations of the field significantly affect the ferromagnetic resonance spectra. It alters the number of most intense lines in the spectra and their frequency range. When additional magnetic layer is added to the CSN, the magnetostatic coupling between the elements leads to additional modes splitting, Fig. 2. Thus, the CSN-s can support 3D magnonic circuits at nanoscale, which operate at wide range of frequencies, offer multimode operation, and promise nonreciprocal effects. 
The research has received founding from the NCN Poland, project no 2020/39/I/ST3/02413.
**References** [1] A. V. Chumak et al., Advances in Magnetics Roadmap on Spin-Wave Computing, IEEE Trans. Magn. 58, 1 (2022).
[2] A. May, et al., Realisation of a frustrated 3D magnetic nanowire lattice. Commun. Phys. 2, 13 (2019). 

![](https://s3.eu-west-1.amazonaws.com/underline.prod/uploads/markdown_image/1/image/6188d565ba7c5e1f93f8bd16ea6986c0.png)

Control of the spin wave spectra by magnetic field orientation and magnitude in crescent

We demonstrate field-free spin–orbit torque (SOT) switching in a perpendicular CoFeB/Ta/CoFeB tri-layer device through manipulation of inter-layer exchange coupling.
This finding is based on experimental and simulation results. In the Ta thickness range of 0.5~3 nm, the device exhibited a clear Ruderman–Kittel–Kasuya–Yosida (RKKY) oscillation
where the anisotropy can be modulated. This resulted in a tilted magnetic moment and thus created a tunable SOT switching window. We found that the SOT switching current density (Jc)also appeared to vary with the Ta thickness (tTa). By cross-tuning the anisotropy and Jc with Ta spacer thickness, field-free SOT can be enabled in this tri-layer system. With microspin
simulation we show that, when the out-of-plane spin polarization from the pinned layer generated a torque that broke the symmetry of the free layer, precession could be enabled along the
x-y plane. This made it possible to achieve perpendicular magnetization switching without an external magnetic field by overcoming the damping torque. Through simulations we also
confirm that the Neel orange peel effect became non-negligible due to interface roughness and coupling effect in the presence of perpendicular anisotropy. Fortunately, the Neel field
induced by the Neel orange peel effect was found to favor the zero-field reversal.

![](https://s3.eu-west-1.amazonaws.com/underline.prod/uploads/markdown_image/1/image/d48fdd084dc33e5c48203077cab98f69.png) 

Fig.1 (a) Schematic illustration of the Ta/MgO(1)/CoFeB(1.2)/Ta(1.0)/CoFeB(1.2)/MgO(1)/Ta (thickness in nanometer) Hall bar device and corresponding measurement configuration. (b)
Hall resistance (RHall) v.s. perpendicular magnetic field (Hz) for the proposed device with varying tTa. (c) Current-induced magnetic switching with varying tTa. (d) Upper figure: macrosimulated Mz v.s. Jc with M1 tilting from +Z to +Y by 20 deg. but M2 lying perfectly along +Z direction; lower figure: simulated Mz v.s. Jc with M1 lying along + Z direction but M2
tilting from + Z to + Y by 20 deg. (e) micro-simulated switching of the proposed device; left: both M1 and M2 with (001) alignment; right: M1 with (001) but M2 with (0, cos5°, sin5°)
alignment. Snapshots of the magnetization reversal configurations corresponding to the two switching conditions, which were taken at ~4.9 ns (marked by vertical dashed lines).

Field free CoFeB/Ta/CoFeB SOT Devices Achieved by Modulating Spacer Thickness:Simulation and Experiment

Patterned FePt media solutions, such as Bit-Patterned Media (BPM) and Embedded Hardmask Patterning (EMP), have been proposed as alternative methods to improve Heat-Assisted Magnetic Recording areal density. Understanding etching mechanism of FePt material is important to warrent the low damage to the magnetic properties caused by micro-fabrication process. In this research, Reactive Molecular Dynamics (MD) modeling is carried out to study methanol (MeOH) plasma etch on L10-FePt media. The atomistic-level etch simulation process is divided into two sequential MD simulation steps: the radical-based reactive treatment step, followed by the ion-based physical etch step. Carbon-monoxide (CO) and H2 molecules are identified as the main etch precursors in methanol plasma interacting with substrate. Reactive interaction between CO/H2 radicals and Fe/Pt atoms is studied using bond-order ReaxFF force field with atomic charge calculation. Bond energy calculation shows the positively charged Fe and Pt and the negatively charged C atoms in CO molecules can form ionic carbonyl bonds that are shown more stable than Fe-Pt metallic bonds. As the result, it is found that the number of Fe(CO) and Pt(CO) carbonyl bonds are dominated among the new bonds produced after the reactive-treatment process. In the following physical etch step simulated with Ar or He ion bombardment, in comparison with FePt surface without CO/H2 treatment, the sputter yield of FePt can significantly improve by 2-4X on the samples with the CO/H2-treatment step. 
**References** 
[1] H. Wang, H. Zhao, P. Quarterman, and J.-P. Wang, Appl. Phys. Lett., vol. 102, no. 5, p. 052406, 2013 
[2] Patent: US10,347,467B2, J.-P. Wang, P. Quarterman and J. Zhu 
[3] LAMMPS - A flexible simulation tool for particle-based materials modeling at the atomic, meso, and continuum scales, Comp. Phys. Comm. (accepted 09/2021),
DOI:10.1016/j.cpc.2021.108171 
[4] J. Zhu, P. Quarterman, J.-P. Wang, AIP Advances 2017, 7 (5) , 056507. https://doi.org/10.1063/1.4977223 
![](https://s3.eu-west-1.amazonaws.com/underline.prod/uploads/markdown_image/1/image/a01666868c95347f3bf6c30ec19d4fec.png) 
Figure 1. Number and types of carbonyl bonds created on FePt surface after CO/H2 exposure

![](https://s3.eu-west-1.amazonaws.com/underline.prod/uploads/markdown_image/1/image/535be17232038eb114b6084ff7a87b38.png) 
Figure 2. FePt sputter yield ( with Ar ions) comparison on CO/H2-treated and non-treated surface

Reactive Molecular Dynamics Modeling of Plasma Etching of L10 FePt Magnetic Media

L10 ordered FeNi alloy is considered as a promising candidate for rare-earth-free and environment-friendly permanent magnet. Highly ordered single-phase L10 FeNi is challenging to synthesize due to its low chemical order-disorder transition temperature. Recently, a nonequilibrium synthetic route utilizing a nitrogen topotactic reaction was considered as a valid approach although the detailed phase transformation mechanism is missing.[1] In this work, we investigated the formation mechanism of the tetragonal FeNiN precursor phase during the nitridation of FeNi nanopowders. [2] 
A low oxygen induction thermal plasma system was applied to synthesize the FeNi nanopowders (NPs). The processed FeNi NPs were annealed under a hydrogen gas flow at 1 L/min for 2 h at 400 °C. Then, the NPs were nitrided at 350 °C under ammonia with gas flowing at 2 L/min for 16 h. The detailed microstructure analysis was performed with an atomic resolution analytical electron microscope JEM ARM200F. 
High-resolution TEM observation reveals intensive nanotwins in the nitrided FeNi NPs which results in a distorted lattice Interestingly Fe segregates at the TBs was confirmed with EDS mapping. Thus, the nanotwins region may provide preferential nucleation sites for the FeNiN product phase in the Fe2Ni2N parent matrix Furthermore, detailed microstructure characterization shown in Fig.1 revealed that the growth of the FeNiN product phase followed a massive transformation with high index irrational orientation relationships and ledgewise growth motion characteristics detected at the FeNiN/Fe2Ni2N migrating interface. Based on the results, we delineated a potential formation route of the FeNiN precursor phase in the FeNi NPs during nitridation. 
**Acknowledgment:** 
This work was partially supported by the project Development of Magnetic Material Technology for High Efficiency Motors which was commissioned by Japan's New Energy and Industrial Technology Development Organization (NEDO). 
**References:** 1) G oto, S. et al. Synthesis of single-phase L10 FeNi magnet powder by nitrogen insertion and topotactic extraction.
Sci Rep 7, 13216, doi:10.1038/s41598 017 135622 (2017). 
2) Wang, J., Hirayama, Y., Liu, Z. et al. Massive transformation in FeNi nanopowders with nanotwin assisted
nitridation. Sci Rep 12, 3679, doi.org/10.1038/s41598-022-07479-8 (2022). 

![](https://s3.eu-west-1.amazonaws.com/underline.prod/uploads/markdown_image/1/image/7799f041271182e5315509ee10844611.png) 
Fig. 1. ABF-STEM images of nitrided FeNi NPs with terraces/ledges demonstrating the ledgewise growth motion of the FeNiN/Fe2Ni2N interface (a & b). (c) schematizes the representative high-index orientation relationship present in (b).[2]

Nanotwins assisted nitridation in FeNi nanopowders synthesized by induction thermal plasma

The interplay between geometry and topology of the order parameter is crucial properties in soft and condensed matter physics, including cell membranes [1], nematic crystals [2,3], superfluids [4], semiconductors [5], ferromagnets [6] and superconductors [7]. Until recently, in the case of magentism, the influence of the geometry on the magnetization vector fields was addressed primarily by the design of the sample boundaries, aiming to tailor anisotropy of the samples. With the development of novel fabrication techniques allowing to realize complex 3D architectures, not only boundary effects, but also local curvatures can be addressed rigorously for the case of ferromagnets and antiferromagnets. It is shown that curvature governs the appearance of geometry-induced chiral and anisotropic responses [6-8]. Here we provide experimental confirmations of the existence of local and non-local curvature-induced chiral interactions of the exchange and magnetostatic origin in conventional soft ferromagnetic materials. Namely, we will present the experimental validation of the appearance of exchange-driven Dzyaloshinskii-Moriya interaction interaction (DMI, local effect) for the case of conventional achiral yet geometrically curved magnetic materials [9,10]. This curvature induced DMI is predicted to stabilize skyrmions [11] and skyrmionium states [12]. Furthermore, we will address the impact of nonlocal magnetostatic interaction on the properties of curvilinear ferromagnets, which enables the stabilization of topological magnetic textures [13,14], realization of high-speed magnetic racetracks [15] and curvature-induced asymmetric spin-wave dispersions in nanotubes [16]. Furthermore, symmetry analysis demonstrates the possibility to generate a fundamentally new chiral symmetry breaking effect, which is essentially nonlocal [13]. Thus, geometric curvature of thin films and nanowires is envisioned as a toolbox to create artificial chiral nanostructures from achiral magnetic materials.

Local and Nonlocal Curvature induced Chiral Effects in Nanomagnetism

Artificial spin-ice systems permit the design and study of a wide family of emergent physical phenomena resulting from the combination of a very large number of interactions between simple elements. They are of great interest since the arrangement of elements, as well as their interactions, can be tuned by means of relatively simple lithography.
An important challenge in the study of artificial spin-ice systems is the large number of elements involved in each system, in combination with their small physical size. Techniques such as magnetic force microscopy or X-ray microscopy are usually needed to study them. In addition, due to the dynamic and/or stochastic nature of the emerging phenomena, also a large number of states of the system need to be probed in order to have a complete physical picture of the system, or to reduce enough the uncertainty in measurements of stochasticity parameters. Finding the right balance between spatial resolution, speed and availability of experimental facilities is therefore an exciting endeavour.
In this talk, we will discuss our experience with the optimization of full-field Kerr microscopy at high resolution and throughput (number of images), presenting the technique as an attractive option for the study of artificial spin-ice systems. We will present the key technical components necessary to perform this type of experiments, and, in particular, how to produce very large datasets volumes that can subsequently be employed to extract complex physical parameters via statistical analysis. See, for example, the use of automatic switch detection in Figures 1 and 2, in which 16 triangular honeycomb lattices are imaged in parallel (Figure 1) and the switching of vertical elements is automatically extracted from differential Kerr contrast (Figure 2). We will use our recent demonstration of the tunability of stochastic domain-wall decisions in honeycomb lattices using >200,000 images [1] as an example to guide the discussion.
We anticipate a great interest from the artificial spin-ice community, as the size of individual elements in artificial spin-ice networks often falls within the resolution limit of the technique (≈150nm). This could open the door to exploring statistical physics and new device applications with a level of detail hardly reachable until now. 

**References:** 

[1] Sanz-Hernández, D., Massouras, M., Reyren, N., Rougemaille, N., Schánilec, V., Bouzehouane, K., Hehn, M., Canals, B., Querlioz, D., Grollier, J. and Montaigne, F., 2021. Tunable stochasticity in an artificial spin network. Advanced Materials, 33(17), p.2008135. 

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